Metal caskets, and in particular steel caskets, upon being buried are subject to the effects of ground water. Depending on the location of burial, the ground water may contain salt or other minerals. Exposure to such ground water provides a corrosive potential which becomes actual upon the deterioration of the casket finish and the ultimate exposure of the bare metal to the elements.
Caskets have been provided with protection against corrosion by electrically connecting a sacrificial anode to the casket, whereby the casket becomes the cathode of an electrolytic cell in the presence of ground water. This sacrificial anode may be made of zinc, aluminum, magnesium or any other metal of higher electromotive potential than that of the cathode (casket).
One prior solution aimed at providing cathodic protection to a burial casket is disclosed in Hillenbrand U.S. Pat. No. 3,052,946, for "Burial Casket," issued Sept. 11, 1962 and assigned to the assignee of the present invention, the entire substance of which is hereby incorporated by reference herein as if fully set forth in its entirety. In that patent, there is disclosed a sacrificial anode rod mounted in a groove or recess in the bottom of the casket. A metal yoke is attached to either end of the anode rod. The ends of the yokes are attached to the casket recess by soldering or welding. The anode rod is electrically insulated from the casket over its length by wrapping the rod with insulating tape. An electrical resistor has one lead connecting the resistor to the core wire of the anode rod, and another lead connecting the resistor to the yoke to provide electrical connection between the casket and anode rod and through the resistor. The resistor provides a resistance in the circuit of an electrode cell comprised of the exposed metal of the casket, the sacrificial anode and the ground water. The resistor controls and limits the current flow through the circuit and hence retards or limits the rate at which the sacrificial anode is consumed after activation of the cell by deterioration of the casket finish.
The resistor mounting has been one area of the cathodic protection system which limits the reliability of the system. Specifically, the resistor, being somewhat delicately attached to the anode rod and casket, is subject to becoming snagged and pulled loose from the connection to the anode rod, the connection to the casket, or both, during fabrication, transport and the like of the casket. In addition, the resistor is subject to shorting if its leads come into contact with the casket bottom or the metal straps which are sometimes used to attach the anode rod to the casket bottom.
One prior attempt at improving the reliability of the casket cathodic protection system by protecting the resistor from damage has been to provide the steel strap which secures to the casket bottom the end of the anode rod, having the resistor attached, with a protecting tab portion which extends laterally from the bracket. The protecting tab portion extends over the resistor thus providing protection to the resistor from obstacles below the casket. The underneath, or resistor facing, side of the protecting tab is provided with insulative tape to prevent the resistor leads from shorting against the protecting tab portion of the steel strap. However, such a protection measure does not provide any protection to the resistor against its leads becoming forced against the bottom of the casket, and thereby shorting the resistor out. In addition, application of the insulating tape to the protective tab portion is somewhat difficult and cumbersome, and if the tape becomes nicked the bare metal of the protective tab portion can become exposed to the resistor leads thus presenting the possibility of shorting.
Another area of such casket cathodic protection systems which limits their reliability is the method of insulating the anode rod from the bottom of the casket and from the aforementioned metal straps sometimes used to attach the anode rod to the casket bottom. Such has taken the form of wrapping the anode rod with insulating tape. As discussed above, while not only being somewhat difficult and cumbersome to apply, the insulating tape has a tendency to become nicked thus exposing the anode rod to the casket bottom and/or the metal straps. Such nicks leave the anode rod susceptible to being shorted out at those points which leads to premature consumption of the anode rod.
It is therefore a main objective of the present invention to provide a cathodic protection system for a burial casket with improved reliability.
It is another objective of the present invention to provide for improved protection of the resistor element in a burial casket cathodic protection system.
It is yet another objective of the present invention to provide an improved means of insulating the anode rod and resistor from shorting out in a burial casket cathodic protection system.